DISCLAIMER: The cases / examples on this blog have been anonymised to maintain confidentiality of patients. Cases have been acquired from various international hospitals and through other medical colleagues with the intention to teach through case examples.

Wednesday, 12 November 2008

I am sorry for setting you such a difficult case but all of the information to work out the case lies in the history, examination, radiology and microbiological results.

Firstly, in order to work out the case, the hidden clues lie in the fact that although the patient is only slightly confused and her mini-mental state examination reveals a pretty good cognitive state, she is most likely able to answer further questions to derive more history.

So, let's go through each question and answer in turn:

Questions:

1) What does the Skull Xray show?

The skull Xray shows a vertical, linear metallic object in a vertical plane on the lateral view of the patient. There is also evidence of previous dental work because of the metallic fillings present and absence of teeth!

2) How will you try to work out the cause of the abnormality?

In dealing with the main abnormality, which is the vertical metallic object, the history and physical examination are there to guide you. There is no evidence of any head trauma and no history of any cranial surgery. Hence, is the metallic object actually inside this lady's skull or on the surface of her skull? Remember, an X-ray in one plain does not always give you the location of an abnormality. An anteroposterior film would also be needed to locate the abnormality.

However, there is an even easier way to establish the cause of the abnormality in this patient. First of all, if the patient had severe confusion and could not answer questions then a simple physical examination of the scalp for a metaliic object would be in order.

However, this patient can answer questions. All that was done was to ask the patient "Do you wear hairpins?" -- the patient replied "yes, all the time". Examination revealed no hairpin as it had been removed by the thorough nursing staff before her head CT scan!

Hence, the hairpin is a 'Red Herring' put in to divert your attention away from the real problem that follows next! Sorry!! :-oHence, history, history and history again wins the day. Ask the patient! This avoids expensive scans and radiation exposure..... :-)

3) What could be the cause of the positive blood cultures?

This patient has a history of aortic stenosis and atrial fibrillation. Both these conditions can predispose to collapse and even more so in combination. Moreover, she is using Ramipril which is contraindicated in severe aortic stenosis because it can result in hypotension. The warfarin is also another potential concern in respect of unrecognised haemorrhage which could be gastrointestinal or intracerebral as likely foci to result in sudden collapse.

The history of a peptic ulcer compounds the suspicion of a possible GI bleed on warfarin. However, there was no complaint of abdominal pain or malena although not all elderly patients experience painful GI haemorrhage nor do they develop malaena in the early stages.

The fact that the patient has no neurological signs makes a massive stroke less likely although a small subarachnoid bleed is still possible but there was no 'thunder clap' headache making this diagnosis somewhat tenuous. The CT head scan revealed no infarct, bleed or SAH. There was no intra-cranial metallic foreign body either! :-)

The real clue lies in the fact that the patient has a fever and positive blood cultures formed of chains of streptococci and she has a cardiac murmur. One must always consider infective endocarditis as a hidden source of infection and vegetations can embolise during anticoagulation therapy (although as mentioned, in this patient there were no localising signs in the neurological examination).

The Xray of the skull comes back to tell us that this lady has dental disease -- she has had multiple tooth extractions! Streptococci in chains might suggest oral streptococci.Of course, other sources of strepococci can come from the pharynx, middle ears, skin (cellulitis) etc but the patient complained of no such symptoms in any of those areas and the physical examination revealed no evidence of these possibilities.

The fact the patient might have a superimposed infection (i.e. sepsis) on a background of aortic stenosis, atrial fibrillation and on an ACE-inhibitor would be sufficient reason to predispose this patient to a collapsing episode. However, a small stroke and subsequent seizure e.g. from a septic emboli, might just as well cause a collapse. As in all elderly patients, silent acute coronary syndrome (ACS) should always be ruled out (please see my previous blog entries).

4) How will you determine the predisposing cause?

Again, ask the patient !!! This patient admitted that she had a tooth extraction 2 weeks before her collapse for dental disease and for fitting a new set of dentures. She was not given prophylactic antibiotics.

The fact that the patient had an aortic murmur could be due to aBicuspid Aortic valve which is a risk factor for endocarditis. Without a dentist knowing about a cardiac murmur they cannot be expected to give prophylactic antibiotics.

It is very important to inform all patients if they have a murmur so that they can inform their dentist such that antibiotics can be given prophylactically during dental procedures.

In this case, the lady underwent a transthoracic cardiac echo which did not reveal a vegetation. The aortic valve area was and gradient were consistent with only mild aortic stenosis.

However, during her admission, she complained of several episodes of central chest pain at rest that were gripping in nature with subsequent ECG changes and a mild tropinin T rise (0.15). It is entirely feasible that an additional potential cause of collapse was indeed a silent acute coronary syndrome although this is not supported by her admission ECG nor is it supported by a previosuly normal troponin T test. Another potential cause of coronary ischaemia is coronary artery emboli from a vegetation.

This patient also unwent cranial MRI imaging which revealed 3 fresh small infarctions that were not visible by CT, consistent with septic emboli.

The above Diffusion MRI picture shows a 'bright' area consistent with a new infarction.In the above MRI picture, a midline bright dot is consistent with a new infarction.

In the above MRI picture, an asymmetric frontal lobe lesion is again consistent with a new infarction.

In view that the eventual culture results grew Streptococcus Lancefield Group G this would be very consistent with a picture of infective endocarditis as was suspected at the bedside on the morning of the admission.

This lady meets the criteria for definite I.E. with one major criteria (positive blood cultures with an organism known to cause I.E), and three minor criteria (Temp >38 degrees C during her admission, embolic phenomena and a predisposing heart condition i.e. abnormal cardiac valve).

This is the second case I have come across in the last few years whereby I.E. has been diagnosed using the modified Duke's criteria with an absence of obvious vegetation. For the other case, please visit this link.

This was followed up by a transoesophageal echo which showed aortic stenosis and mild mitral regurgitation but no vegetation was seen. This however, does not rule out infective endocarditis.

In view of the history, examination, lab tests, microbiology and MRI result, it is most likely that the vegetation embolised to the patient's brain resulting in there being no visible evidence on the heart valve.

The patient was commenced on penicillin G and gentamicin for this fully sensitive organism.

This patient chose not to undergo coronary artery investigations.

Group G Streptococcal Endocarditis

The usual cause of a streptococcal I.E. has classically been by Group A Strep (GAS) although in recent years Group C and G have also been found to cause I.E. In fact, both Group C and G strep produce disease in a very similar way to the GAS and can be considered en bloc.

Group G strep can be found in the oral cavity and there have been several case reports of it causing I.E. especially on abnormal cardiac valves.

Moreover, Group G Strep I.E. has been documented to have a higher risk of embolisation than other forms of I.E. as has been found in this case.

Professor Gerald H Stein, University of Florida, kindly answered this case and got the 'nail' on the head! Well done. Here are his comments:

1. Skull xp shows a metal object which could be an artifact- an object outside of the skull such as a woman's hair pin. Upper dentures are also seen. C 3 has an anterior osteophyte. No skull Fx in the single view provided.

2. To prove my idea of the metallic object, I would examine her scalp to search for the object, and if not found, ask her about a prior reason for any such intra-cranial object. It is bad form to have only 1 skull view; multi-projections are required in every case of skull xp's.

3. Strep in 4 BC's= a septic source. The axillary fever would be about 38 *C if taken orally. Her mild confusion/delirium is likely from the sepsis. Most likely source is infectious endocarditis.However, more than 1 source is possible. In this case with mild confusion and fever an LP is indicated to rule out co-existing bacterial meningitis. Septic brain emboli are a real possibility. Best to perform brain CT to r/o skull Fx and brain abscess before LP

4. TTE for vegetation on aortic or less likely mitral valve+ assess degrees of aortic stenosis. Warfarin may exacerbate the septic emboli shower. Urinalysis for RBC and RBC casts + rheumatoid factor are indicated. These are sometimes + in IE.

An anonymous comment was received which is below. Thank you to this person who contributed their answers to this difficult case.

1) What does the Xray show?

I would say that there is something metallic in the skull and that seems going through the base of the cranium into inside. In addition, there appears to be a part where the continuity of the bone is lost.However, any evidence of trauma was not found on physical examination and history, therefore there is probably no fracture.

2) How to work out the cause of the abnormality

At first, I would like to see the nasopharynx. If something penetrated the cranium, I might be able to observe some abnormality at its entrance. Fiber scopes would be useful.With or without any information I could get from it, I will order head CT to get more information. This patient possibly have brain abscesses or hemorrhages.In addition, cardiac echo is required to find the clue of IE or clot .

3) What could be the cause of the positive blood cultures

IE (infectious endocarditis) orinfection through foreign bodies

4) How to determine the predisposing cause

To be honest, I have no idea, but I am worried about her multiple medications and renal failure. If her confused status is thought to derive from digitalis intoxication, ECG, electrolytes, drug concentration would be helpful.Regarding IE, the predisposing cause may be cardiac valve diseases or poor oral hygiene.

The Moral of This Case

What you initially see is not always what it is. Once all usual causes of an abnormality have been ruled out, no matter how unusual or obscure it may seem, what is left may indeed be the problem.

Go back to basics. Find out by asking the patient and looking, and if necessary, take that extra AP plain view of the skull to be certain. More advanced radiology should only be ordered if there is a reason to do so, for example, in this case there was a real suspicion of septic emboli. The fact that an MRI of the brain was performed means by definition that there was no intracranial metallic object!

Risk factors for new disease can sometimes be inferred by the presence of existing diseases e.g. aortic stenosis, and physical examination findings, but at the end of the day, it is the history from the patient that gives you the real information.If you don't have the data for a patient then go back to the bedside and take more history.

Medicine is not an exact science. You need to be a medical Sherlock Holmes and find the clues that lead you to the answer. It may not happen all in one go but gradually, gradually the answer may come from the patient to make everything more clear.

Dental Prophylaxis

Although the AHA guidelines for prophylaxis for endocarditis changed in 2007, the recommendations for high risk procedures causing bacteraemia are still firmly in place.

Dental treatment is a high risk procedure whereby manipulation of the gum tissue, penetration of the tooth substance or oral mucosal breach can result in entry into the systemic circulation of oral commensal bacteria resulting in infective endocarditis, usually on an abnormal valve.

Hence, prophylactic antibiotic options include:

Amoxicillin, 2 g orally 30 to 60 minutes before the procedure; a second dose is currently not longer recommended.

Alternative regimens are still given 30 - 60 mins before the procedure and include: